Any decent paint shop can colour match your car, taking the petrol cap flap off and into the shop is what most people, better than buying a standard colour paint as being matched it will take into account any fading over the years.

The original "Datenkarten" or "Data-card" would also state this info.
Your local dealer can contact MB-Classic Center also, and get the proper information..
(A full restoration could have ment a color upgrade)